Method of and means for producing an optical illusion



P. TI TIBBLES. METHOD 0F AND MEANS FOR PRODUCING AN OPTICAL ILLUSION.

APPLICATION FILED 0CT.27| I920.

2 SHEETS-SHEET I I Fl G. 5.

Patented Aug. 16, 1921.

P. T. TIBBLES.

METHOD or AND MEANS Foa PRonumNG AN OPTICAL lLLusloN.

APPLICATION FILED OCT. 27, 1920. 1,387,681. Patented Aug. 16, 1921.

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UNITED STATES PATENT oFFlcE.

METHOD OF AND MEANS FOR PRODUCING A N' OPTICAL ILLUSION.

Specification of Letters Patent.

Patented Aug. 16, 1921.

Application filed October 27, 1920. Serial No. 419,930.

To all w/lzomfr'maj/ concern y Be it known that T, Parier THOMAS Tm- BLrs, a subject ot the King of England, residing at 54 High street, Bloomsbury, London, XV. C., England, have invented certain new and useful Improvements in Methods ot and lfieans for Producing Optical Illusions, ot which vthe `following is a specification.

The present invention relates to a new method oi and means t'or producing an optical illusion consisting in changing an illuminated picture, design, or like elect in such a manner that the means by which the change is produced are and remain invisible to a spectator placed in front ot the picture. The change preferably relates to both the design or composition and the colors of the picture, and may be eiiec'ted gradually whereby very artist-ic and original etiects are produced. The picture to be changed is eX- ecuted in such a .ianner as to be semi-transparentor translucent and become morey visible to the eye ot the spectator when illuminated from behind. Between the picture and the source ot light, which may be placed behind the picture and at a comparatively small distance from it, are movably arranged one or more translucent or semitransparent pictures which will hereafter be called masks These masks are, if suiciently removed from the front picture, hereinafter called picture, and from one another, invisible to the spectator who is located in iront ot the picture, although they remain between the picture and the source of light and are illuminated by the latter. They become visible to the spectator when they are brought close to the picture. This phenomenon is rather surprising', particularly in view ot the tact that the picture is illuminated trom behind by light passing through the masks, and the phenomenon occurs even if a strong and rather concentrated source ot light, for instance an electric lilament lamp of high power is used at a rather short distance and centrally behind the picture and the masks. Then the first mask is moved toward the picture it becomes gradually visible, not as a separate effect but as an additional eii'ect superimposed upon the picture, that is to say the spectator can see only the composite effect of the picture and the iirst mask both as regards the drawing or design and the colors, and he will therefore have the impression that the picture has gradually changed in design and color.

-i similar eiiect is produced by bringing the second mask close u p to the first mask,.and so on. The reverse change is produced by moving gradually the masks away from the picture, starting with the last mask. It may be pointed out that a very small movement is suiiicient to make a mask effective or ineffective and it is therefore necessary when a mask is being removed, that is moved away i'rom the preceding mask, to hold the other masks close to one another and the picture.

It the invention is used for advertising purposes the changing of the picture may be continuous, that is the masks may be advanced toward the picture, then moved away in the reverse order, advanced again and so on, and the movement of the masks may be produced by a motor or a clockwork mechanism or in any other suitable manner. It it is not desired to change the picture in both senses, that is by first superimposing the effects of the masks and then removing the superimposed effects one by one, all the masks may be moved away from the picture simultaneously and if desired the light may be extinguished or covered during this time. Or the opposite effect only may be produced by exhibiting lirst the picture with the masks in their operative positions, that is brought up quite close to and preferably in Contact with the picture and one another, and then gradually removing the masks starting with the last or back mask. In this case the light may be covered or turned oil" during the reverse operation, that is while the masks are brought back into operative position.

The invention may be used for educational purposes, ifor instance for demonstrating the growth of a plant. It may also be used tor changing stage scenery, amusement, signaling and various other purposes.

It should be pointed out that while a certain degree ot' transparency is essential for the purposes of the invention, both in the picture and the masks, the actual degree of transparency and the manner in which it is obtained must necessarily depend on the requirements of each particular case, the number ot the masks used, the nature of the co1- ors, the nature of the picture, the light and other factors.

As a rule the picture should be executed on a semi-transparent material such as paper, linen, silk, union, ground glass. Such materials as clear glass, gelatin, Celluloid are rather too transparent and unsuitable but may it desired be used for? the mask. That part ot the picture which it is desired to alter, it painted onY the aicture, should be done in soft light tints. l ard lines and big patches ot vivid colors should as a rule be avoided in the working parts of the picture. The first mask maybe painted or drawn in darker colors and more definite lines than the picture.V The secondy mask may be still darker or more definite than the first, and so on. The greater the transparency or the masks, the larger the number that may be employed. It is necessary to use transparent colors for the picture, and also the masks, although. to a lesser degree, and a rather convenient way of putting on the colors is by means oit'. an aerograph. lt is possible te use an opaque or pigment color :tor someportions of a mask provided that such portions are so situated that as the mask moves away from the picture and nearer to the light, sufficient light can filter through the unpainted or semi-transparently painted parts ot the mask to obliterate theel'ects et the opaquely painted part. It might also in some cases be preferred to have opaque portions on the picture, for instance it' the picture is made oi several sections, in order to cover up the joints, or il the mask is made of several sect-ions. Particularly in applying the invention to stagescenery, it may be necessary to make up the device in sections, joining two or more sections together and operating the masks separately or together. i Itis important thatthe masks should all lit tightly against the back of the picture at the same time, to give clear definition to the whole or composite effect when illuminated. The changing etect starts immediately any one mask is separated from another mask or from the picture by the mere'st traction ot an inch. While the back mask is being moved the other masks must be held rigidly against the picture, until it is the turn of the next mask to move, and so on. The distance a mask must be withdrawn to obliterate completely its effect upon the picture usually varies from one to tour inches, but this largely depends upon the visibility of the color used. A patch oi vivid green, tor eX- ample,`rcquires a greater disappearing distance than a similar patch et pink. The colors that disappear easiest should be 'reservedV 'tor the mask-or masks nearest the picture. In addition to changing the design ot a picture it is possible to change the colors, or the colors alone may be changed. For instance the change may consist in showing awom'an dressed in a white gown l that changes its shade through the whole range of tints to a black. It may be pointed out that the colors in the different masks and by the movement o'tl a mask,

the picture are combined by the light behind in much the same way as an artist will mix primary colors to produce other shades. As one color separates from or joins the others so the prevailino' tint of the combination changes. By this means, two or three masks will produce the effect of a larger number ot color changes. Printed words can be added to or changed in the same way as any other design.

As regards the relative movement ot the masks toward and from the picture, it may of course be oi any suitable kind, tor instance the mask may be moved parallel to the picture in a direction at right angles thereto, or they may be hinged to the picture and swung into or away from the effective positions. That part of the rear mask which is nearest the hinge comes into view first when the masks approach and is the last to disappear whenA the masks separate. A gradual change in a certain direction may in' many cases be preferable to a simultaneous change of thev whole surface of the picture, as it may be more easilyiollowed by the eye'. By bringing successive masks alten nately at the top and the bottom the direction of the change may be varied. By this means it is torl instance possible to show the picture' lof a dressed woman changing first her boots, then her gloves and lastly her hat. It the movement of the masks were parallel, the changes would occur simultaneously.

The accompanying drawings show by way ot example one construction of an apparatus suitable for carrying out the invention.

Figui-el is a front elevation, Fig. 2 a ver tical cross section of the apparatus,'Fig. 3 shows a picture, Fig. l'the iirst mask, Fig. 5 the second mask, Fig. 6 the tliird mask and Fig. 7 the composite eielct of the picture and the three masks, F igs'. 8 to l1 show four successive effects in' a casewhere the perform-` ances'tarts with the lfully developed picture, that is the picture and the three masks brought together, and the change consists in obliterating. Fig, 8 represents the composite eiect, Fig. 9 the e'iect after the last mask has been moved away, Fig. i0 the effect after two masks have been removed, and Fig. llthe picture.

In Figs. land 2, 1 represents a trame or casing Vin which the picture 2 is mounted upon the rear surface of a molding 3. To the molding 3 is hinged at t a .frame 5 upon the Jfront surface of which is mounted the tirst mask 6. To the frame 5 is hinged at 7 `a trame 8 upon which is mounted the second mask 9 as shown. Spiral springs (not shown) may be provided on the hinges to hold the masks 6 and 9 against the picture 2, or other means may be provided for this purpose, for instance Weights. The masks 6 and 9 are connected at the bottom edge by a short piece of chain 10. The mask 9 is connected by a cord or chain 1l passing through an eye 12, to a crank pin 13, the cord being attached to the pin by means of an eye 14. The crank is continuously rotated by means of a pulley 16 and a rope 17 from an electric motor 18 mounted inside the casing, but a clock work or other motor may of course be employed. It will be seen that half a revolution of the crank will first pull the mask 9 away from mask 6 and then through chain 10 the mask 6 from the picture, and that during the next half revolution first mask 6 and then mask 9 will be brought close to the picture by the springs. The source of light is indicated by 20. The back wall 2l may be covered with polished tin to reect and diffuse the light.

This apparatus may also be used in painting the masks. rlhe picture may be first painted on the outer surface or" the material mounted on the molding 3; the rear mask carrier may then be lifted up and the mask 6 may be painted from the inside while in Contact with the picture, and theJ mask 9 may be tin-ally painted from the inside. In this manner perfect registration ot the masks and the picture may be obtained.

It may be pointed out that this invention is restricted to a method and apparatus in which the picture is illuminated from behind by a source of light.

I claim 1- 1. A method of producing an optical illusion by changing the picture design or like effect characterized by the fact that semitransparent mask or masks are gradually moved toward and away from the picture and between the picture and a source of light, substantially as described.

2. A method for producing an optical illusion according to claim 1 further characterized by the fact that the masks are gradually moved angularly toward or away from the picture, and between the picture and a source of light substantially as described.

3. An apparatus for producing an optical illusion consisting in changing an illuminated picture, design or like effect, comprising a semi-transparent picture, one or more semi-transparent masks adapted to be gradually moved into close contact with the picture and one another and away from the picture and one another, and a source of light arranged behind the mask or masks from the picture, substantially as described.

4. An apparatus for producing an optical illusion consisting in changing an illumi` nated picture, design or like effect, comprising a semi-transparent picture, one or more semi-transparent masks adapted to be gradually moved into close contact with the picture and one another and away from the picture and one another, and a source ofv strong artificial light between which and the picture the mask or masks are so moved, substantially as described.

In testimony whereof I have hereunto set my hand in the presence ot two Witnesses.

PERCY THOMAS TIBBLES.

Witnesses:

E. CHALDncorr, I. Mo. GrBoN. 

